As world’s oldest lightbulb turns 125 years old, conspiracy theorists have a 'cover up' theory

Image credit: X (Twitter)​A light bulb has been glowing for the past 125 years. The milestone is once again drawing attention, not only for its longevity but also because conspiracy theorists claim it exposes a decades-long "cover-up" by major light bulb manufacturers. The Centennial Bulb in Livermore, California, is frequently cited as evidence that companies deliberately reduced the lifespan of light bulbs through planned obsolescence, although engineers and historians say its unusual design tells a different story.​According to a Popular Science report, the renewed discussion comes as the Centennial Bulb marks 125 years since it was first switched on in 1901. While the "cover-up" theory points to the light's unusually long life compared with modern incandescent bulbs, experts say its low power consumption, dim output and unique construction explain why it has continued operating for so long, rather than proving that manufacturers intentionally hid longer-lasting technology.​Why the Centennial Bulb has lasted so long​The Centennial Bulb was manufactured by Ohio-based Shelby Electric Company in 1901 and has remained installed at Livermore Fire Station No. 6 in California. It was recognised by Guinness World Records and Ripley's Believe It or Not in 1972 as the oldest known working light bulb.​Unlike modern incandescent bulbs, which were later standardised to operate at higher brightness, the Centennial Bulb now draws only about four watts of power despite originally being designed as a 60-watt bulb. Because it operates at a much lower temperature, its tungsten filament deteriorates far more slowly than that of a conventional incandescent lamp.​Early incandescent bulbs were handmade, and manufacturers often prioritised durability over brightness. Their filaments were enclosed inside sealed glass bulbs, where an electric current heated the metal until it emitted visible light. However, increasing brightness also increased filament temperature, accelerating wear and shortening the bulb's lifespan.​How the Phoebus Cartel fuelled the conspiracy theory​The bulb is often linked to the Phoebus Cartel, an alliance formed in 1925 by lighting companies including Philips and General Electric. The group agreed to standardise incandescent bulbs with an expected lifespan of around 1,000 hours while also fixing prices across markets.​Because the Centennial Bulb has reportedly operated for more than one million hours, conspiracy theorists argue it proves manufacturers intentionally reduced product lifespans as part of a long-running planned obsolescence strategy.​However, researchers and electronics experts note that the comparison overlooks major differences in performance. The Centennial Bulb emits only a faint glow and consumes significantly less power than a standard incandescent bulb, making it unsuitable as a practical household light source.​One explanation proposed by electronics and software blogger Maurycy suggests the bulb may have been manufactured with unusually high filament resistance, effectively turning it into a long-lasting night light rather than a bright everyday lamp.​Why modern bulbs took a different path​Lighting technology has evolved by balancing brightness, efficiency and durability rather than maximising lifespan alone. A hotter filament produces brighter, whiter light but also evaporates more quickly, reducing operating life.​The later shift from incandescent bulbs to fluorescent lamps and LEDs further changed the equation. These newer technologies consume less electricity while generally lasting much longer than traditional incandescent bulbs.​Although the Phoebus Cartel established a 1,000-hour standard for incandescent bulbs before dissolving around the start of World War II, experts say the Centennial Bulb's continued operation is primarily due to its unusually dim output and operating conditions, rather than evidence of a hidden manufacturing "cover-up."

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